The present invention relates to a new and improved method of, and apparatus for, producing stacks of flexible, flat products, especially printed products.
In its more particular aspects, the present invention relates to a new and improved method of, and apparatus for, producing stacks of flexible, flat products, especially printed products, by means of which buffer stacks can be formed which serve for intermediate storage of the products and to feed the latter to further processing installations, particularly to feeders or feeding attachments.
In a method of, and apparatus for, producing stacks of products such as is known, for example, from U.S. Pat. No. 3,700,232, granted Oct. 24, 1972, the sheets or pages which arrive in an imbricated formation are taken over by conveyor bands having horizontal conveying direction and arranged in juxtaposed relationship. The products are conveyed against abutment fingers which upwardly project from the conveying path. The first product of the imbricated formation runs up onto the somewhat curved abutment fingers with the leading edge of the printed product and is upwardly deflected. The successive products then are slid upon the related rearmost product of the stack thus formed. In this manner a stack of lying or reposing configuration is formed which grows from the stationary abutment fingers towards the rear and within which the sheets or pages assume an upright position.
The stack thus formed bears upon the continuously circulating conveyor bands. Due to the contact existing between the conveyor bands and the lower edges of the stacked sheets or pages, the same are entrained which has the result that the stack is compressed on the underside thereof. This may result in a fanning of the sheets or pages on the top side of the stack. In order to reduce the friction forces between the conveyor bands and the sheets or pages, depressions are provided in the stack support and extend over part of the length thereof, the conveyor bands extending within the depressions. This measure entails a certain constructional expense and cannot completely eliminate the danger of the fanning of the stack. Due to the continuous abrading passage or sliding of the conveyor bands past the bottom edge of the stacked sheets or pages the latter may additionally become damaged. It should be noted that some frictional entrainment of the stacked sheets or pages by the conveyor bands is desired since otherwise the sheets or pages would assume a progressively more inclined position as the stack grows and would rearwardly slip off the stack.
In the method of, and apparatus for, producing stacks of products as known, for example, from German patent publication No. 2,421,271, published Nov. 28, 1974, the printed sheets which are to be stacked are fed in an imbricated formation to a stationary stacking location by means of a horizontal band conveyor. At the stacking location two deflecting fingers cause the printed sheets to be upwardly deflected at their leading edge. In order to support the deflected printed sheet there are provided support means which are displaceable in correspondence to the increase in the length of the stack and which comprise a support surface inclined at an angle of 45.degree. relative to the horizontal. The first printed sheet is slid onto the support surface while the successive printed sheets are pushed onto the related rearmost printed sheet of the stack.
While there is no danger of a fanning of the stack due to the markedly inclined position of the stacked printed sheets, the latter tend to slip off towards the rear. In order to prevent such slip-off, stops have to be provided which, however, may cause damage to the printed sheets. Furthermore, an inclined position of the printed products at an angle of about 45.degree. in the stack is undesired in certain cases.